The present invention relates to ceramic circuit substrates and to manufacturing methods of ceramic circuit substrates. In particular, this invention relates to the technology for forming conductors such as wires or resistors on the surface of a ceramic material.
With progress in the miniaturization of electronic instruments, ceramic circuit substrates have been used actively. Ceramic circuit substrates are used as hybrid substrates for mounting ICs or ceramic packages. Two methods, namely, the thick film technique and the thin film technique have been principally used in forming conductors on such a substrate. Each of these methods is capable of effecting miniaturization of about 1/10 to 1/3, relative to what is possible using a printed wiring substrate made of resin.
The thick film technique, which uses the printing method, is suited for manufacturing circuit substrates in large quantity at low cost. However, the thick film technique is not suited for the formation of conductors, such as wires, that have a fine line width.
On the other hand, the thin film technique is useful for forming lines having a width as small as about 1 .mu.m, since it employs the photoetching method. However, a thin film technique forms thin films by vapor deposition and sputtering, so that it is difficult to manufacture circuit substrates in large quantity at low cost.
Hence, it is desired to develop a new method that is capable of forming relatively fine conductive lines while satisfying the desire to manufacture circuit substrates in large quantity at low cost.
Further, both the thick and thin film techniques require a long manufacturing process to form the conductive lines, so that problems frequently arise in connection with the expeditious supply of circuit substrates. Moreover, these techniques involve a liquid process, such as the use of pastes or developing solutions in the photoetching method. The administration of liquid processes is complicated from another point of view, in that it may create environmental problems.
Additionally, there is a need to open holes in order to connect both sides of the circuit substrate.